Insert records into a table with a condition in SQL Server 2016 - sql

Question

I have a table that has columns that I want to insert into another table with certain conditions. The closest I could get was using this post.
This is how I want to do it:
if (cnt > 50, avg_account, else null) as avg_account
if (cnt > 50, avg_change, else null) as avg_change
As shown above, I want to insert some columns from Table1 into Table2 and especially avg_account and avg_change columns when cnt column in Table1 is > 50.
I tried the following, I am not getting my desired output using the following code,
SELECT
id, branch, account, total, change,
'avg_account' = CASE
WHEN cnt > 50 THEN avg_account -- How can I refer to avg_account values?
ELSE 'Null'
END,
'avg_change' = CASE
WHEN cnt > 50 THEN avg_change -- How can I refer to avg_change values?
ELSE 'Null'
END
INTO
Table2
FROM
Table1
PRINT ' ' + CONVERT(VARCHAR, ##ROWCOUNT) + ' rows updated'
Is my approach correct? Can I get values as indicated in the code snippet? OR should I use a where clause or subquery?
Any help would be appreciated.

Answer 1

I think this is what you want:
select id, branch, account, total, change,
(case when cnt > 50 then avg_account end) as avg_account,
(case when cnt > 50 then avg_change end) as avg_change
into Table2
from Table1;
Notes:
With no else clause, a case expression returns NULL.
NULL and 'NULL' are not the same thing. The latter is a string. The format is probably what you want.
Only use single quotes for string and date constants. Don't use them for column aliases -- because the distinction between a column name and a string is not always obvious.
Don't escape names that do not need to be escaped.
If you want to filter out rows with a cnt <= 50, then use where rather than case.

Answer 2

another approach is to put your condition into where and use two SQLs
select * into table2 from table1 where cnt > 50
insert into table2
select id, branch, account, total, change, null, null from cnt <= 50
Your original query has several bugs
select id, branch, account, total, change,
CASE WHEN cnt > 50 THEN avg_account
ELSE 'Null'
END,
CASE WHEN cnt > 50 THEN avg_change
ELSE 'Null'
END
into Table2
from Table1

Answer 3

I think you just need a WHERE clause, like:
INSERT INTO TABLE2
(id, branch, account, total, change, avg_account, avg_change)
SELECT
id, branch, account, total, change,
avg_account, avg_change
FROM
TABLE1
WHERE
cnt > 50
I may also me misunderstanding you situation. Can you elaborate a little more?

Answer 4

Almost correct. You actually have the logic correct. Your syntax is your problem:
When you enter 'Null' into your database, it will enter the STRING VALUE 'Null', and NOT the NULL Value. Take the quotes off your Nulls.
select id, branch, account, total, change,
'avg_account' = CASE
WHEN cnt > 50 THEN avg_account
ELSE Null
END,
'avg_change' = CASE
WHEN cnt > 50 THEN avg_change ELSE Null
END
into Table2
from Table1
print ' ' + convert(varchar,##rowcount)+ ' rows updated'
Assuming avg_account and avg_change are columns in table 1.